DTC P1574: Stop Lamp Switch Circuit: Description

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The cruise brake switch and the stop lamp switch are brake pedal inputs to the ECM to determine if the brake pedal is applied or released. Ignition voltage is supplied at the cruise brake switch input to the ECM whenever the ignition is turned on and the brake pedal is released (switch closed). If the brake pedal is applied, the cruise brake switch input at the ECM will go low. The ECM stop lamp switch circuit works in the opposite manner. Battery voltage is supplied at the stop lamp switch input to the ECM whenever the brake pedal is applied (switch closed). If the brake pedal is released, the stop lamp switch input at the ECM will go low. If the stop lamp switch input at the ECM were to open, the switch input would read between 5-7 volts (ECM pull-up voltage). DTC P1574 will set if the cruise brake switch input at the ECM does not change state at least once in a given time during a deceleration event.